Abrading apparatus



Sept. 14; 1943. w. L. KEEPER ABRADING APPARATUS Original Filed March 10, 1938 2 Sheets-Sheet 1 Walier l1. Kegfer. 32543 M r W Sept. 14, 1943. w KE-EFER 2,329,204

ABRADING APPARATUS Originl Filed March 10, 1938 2 Sheets-Sheet 2 l0 lwuwvbo'v Walfier L. Keefer.

g4, bamwm m Patented Sept. 14, 194 3 i I .f1; me BMWN A Walter L. Keefe1",-' Hagerstown, 'Mdfl, assignor to Pangborn Corporation, Hagerstown, Md, a cori notation of Maryland original application March 10,, 1938, Serial. No. 195,138; new Patent No.2,246, 522, dated June" Divided and 'thisapplication June ii v 19 4 1., SBIiaPNO. 399,185

' T reclaims. (or. 51 9) T1 This invention relates toabrading apparatus and is more particularlyconcernedwith machines 'embodying a bladed rotor for-propelling abrasive athigh velocity against articles' to be cleaned. Such machinesinltheir basic form"c omprise a "'roton a feed-spoutfor-abrasive; and transfer mechanism for transferring thelabrasive from This application is a 'division of my applica- "tion Serial No. 195,1355, filed- March 10, l-938jfor .Abrading apparatus now Patent No. 2,246,522.

1 Machines embodying bladed rotorsarelin'com mercial use today which}: although they -repre- Y "sent anadvance' in the art over machine's used heretofore, leave much to be desired fromthe' standpoint of wear of various essential operating parts. For instance, directional-control is" attained in those machines-through the use of acentral stationary reed cage'having a feed slot therein through which abrasive is discharged onto the inner ends of the blades by'means ofa rotatable impeller located in the feed cage. These impellers and cages wear out comparatively jr'apidly 'under the action of the abrasive, and must be removed and replaced by new parts; which entails the expense of the new parts-and also the loss of operating time that is involved while the machine is shut down or dismantled for servicing. In my United States Patent No. 2,116,153, granted I May 3, 1938, I have shown'a bla'cledcentrifugal abrading machine which possesses directional control andyetwhichdoes not employ an impeller, or a slotted stationary feed cage, andit is the'major object of this invention to improve and generally refine such machines. a Y

A further object is to 'providea bladed centrifugal abrading machine including a transfer mechanism comprising a rotatableabrasive ac cumulating cup and a stationary-helical deflecting member fordeflecting the abrasive froi'nithe 'cup onto'the blades. 1 I

I It is another object to providea centrifugal abrading machin with a transfer mechanism comprising'a combined abrasive feeder and deflecting assembly for cooperation Witha. rotary {cup of a bladed centrifugal abrad'ing rotor.

A further objectis to provide a'blajded abrad section of a portion Fig. 2- is a front-elevational view of thekrctor shown inFlg. l with" the: feed spout and deflector .as'sembl y removed' and the abrasive chamber shown in section on the line 2--'12 of Fig. 1;

Fi '31s a fragmental section '-taken substantially on the line 3-3 of Fig. 2.: 1 f

Fig 4 is a longitudinal-section of a further modified f-c-rm ofab'rading-apparatus embodying. thisinvention. =5 .1 5+

Fig. 5 is afront elevation ofthe-rotorof Fig. 4 with thefeed spout anddeflec'torremoved and "the ieed' chamber taken in-section on the line 5450f Fig. 4..

" their neighboring :edges. are beveledas @1114 so ,I'.;Fig. 6 is a diagrammatic-developmentoigaportion of the abrasive chamber'and a portion of the deflector of-liigjek. L. i i. a

Fig: 7'is a front elevation of the'ifeeding sideof 'a-further modified. form of the. invention." I

jFig.28 is a longitudinalssection taken vertically "through the: axis ofthe device. shown in Fig. 7. s

i Fig, 9.-is a fragmentalsectiori taken substantiallya1ongthe line 9-'9 of Fig. 8, and

Fig; 10 is a fragmental section taken onlthe line;llllil of Fig.'9,. .the Isectionbeing turned through an angle of 90?, .theideflector assembly being omitted to more" clearly illustrate the remaining structure.

desired form. Forrthe purpose Of'jiHlISEZati'OI'LI have shown a rotor R secured toa' hub portion l .Ill of ashaft .H byme'ans of .aplurality oi screws ..(not shown) A plurality of: sectorshapedi plates 12" are .deta'chablysecured' to the face of*rotor R'byapluralityofscrews.13; :1: 1

As 'shownin; more detailzinFigi 3, .plates 12 are spaced apart on. theiacezof the rotor and Each bladeB isprovided with an abrasive p pelling' facev i ii and, angabrasive guiding flange =Il'for preventingthe;;abrasive from'escaping across theface of;the.hub 10; or it may-beformed :55

over the free edge of the blade during operation. 7 ,The rotor R maybe .rnadato extend wholly with acentral opening whichj s closed by a wear plate" l8. secured ::in place :"by a capscrew lfl tv'veenthe.innerllends ofjblades B with its' 'axis preferablyin 1 alignment :with' .theaxis of shaft shaped openv suitable manner.

of a feed spout 24, the third elementpftheniar chine, which is stationarily supported in any suitable manner, the lower end thereof being provided with a boss 25 to jwflhich acl'efie'ctorLas sembly D is secured by a cap'screw 26. Deflector assembly D is provided witha helical deflecting flange 21 of increasing radius toward discharge edge 22'. f

Chamber 2! may be secured to rotor R in, any

For ins n it may be .carried by plates l2, i .d sir di i s. .2 and 3, I have illustrated the chamber as provided with .a plurality of arms 3| which are disposed so as 32' are disposed ,rearwardly of each blade, they I are subjected to only a minimum abrading action, especially since the abrasive, issuing from the chamber is. not traveling at a velocity high enoughtoeffect any substantial abrading. If a two disc form of rotor is used, chamberll may be secured directly to the lefthand disc.

In operation, spout 24 is supplied with abrasive 'iriany suitable manner, preferably metered, and from 'a gravity drop to impart the desired initial velocity to the abrasive; The abrasive fed into the spout is discharged upon the inner wall' of chamber 2|, and is quickly picked up and promptly brought up to the .full .peripheral'speed ofxtheinner wall of the chamber. After a pre- .'determined quantity of abrasive has accu'miilated. in chamber 21, it .builds up therein to its angle" of repose-which will face dischargeiedge .22.:ibecause of wall 23. If the feed of abrasive into'the chamber be arrested .at this point, the abrasive will remain on the inside Wall of the chamber.- and will not discharge over edge 22.

53 As" described, "deflector-D comprises 'a flange -21 which ispreierably so shaped that its outer periphery generally conforms to the surface .of

tire ome-shaped layer of abrasive lying in the v Nuts '35 are chamber, and is accordingly a helix of increase ing radius toward discharge edge 220i the chamber; Flange 21 is preferably beveled at its outermost edge to substantially conform withthe angle of repose of the abrasive lying" in the chamber, and preferably extends for approximately three quarters of a revolution, oji 2'10", with the result that the abrasive starts to underg'oan "axial deflection towards discharge edge 22' at'ap'oint' 28, and; is finally deflected over the finally disehara g at ed e 22.

maturely be started down the inclinefrom dis .charging, over the edge ,oftheichambenbefore the proper discharge point is attained. As described iin my above-identified application, such a flange preferably terminates short of point 29 to permit "the abrasive to leave the cup at that point. The

abrasive lying on' the interior of the'chamber is .faccordinglydeflected over the, edge thereof at a predetermined .point in the" rotation of the wheel, andstray ably irzeisprevented from leaving else- I py th l; i deflector. "pen mrh ri'l'iig. 1 is shown as being adjusted topause tlig abrasive to be dislodged from the ed 'ge of the feed chamber at approximately the twelve oclock position. The abrasive is thrown substant ally tan e i lly b reason o he .fact i possesses substantially inorrad a veloci y, and i :a ing a the he inhera esgee .o the 11. e a t e insta o dis har e The d s- .cheree mmedse lzjee grd p ly assum s the term o a slishtlviaa-shaee .coniinuq srib o which i i by the "inn end of li ade as they successively pass throng; I, it is-alsp apparent that a he ah es yfi dis h r n iron: th sha cba st ave ns n-z be same n ra direction a e i ner e ds the b ades it pick d no w th a il ieimi m mi e ti abrasiv picked up is smeot ly an continuously accelerated :by th blades, and. is d schar ed from the enter ends thfi eq -inedown ar d rectio 1 It has been remain pra ti e that al pi ra s the deflector ass mbly ina ti n .0.0 in sedat on. a d war reon s slow. -i3eflector flan e se ve t i, d ily-d scha e t he abra- 3?- Bfi e ie i s oute periphery forms a cone .of'increa iae radius in the direet-ion o theirs.- .Qherge ed he abrasive is aused to tend to continue mere down the incline. The run len h .Q flares e1 c nt ols th moveme t. .or the a asive ros the d ica su face .until :it is Wear .on the ,fie ee i slew be ause the maj r tome impellin the ab a ive til-Ward th dis ha ge ed e is sup: plied b centrifu a force. and the flange only the ab asi e, 7 t F 5 and .5: I :hE E li lllstratfld .an e ree ng a para us similar. t that ust d nseribesi bu t iny lv sahamber whish is i closed erseet ipntbe feedonenine and n epssies er eachr'hlada a lilie dead :rotor R s p ovide wit bla es- 5 in accordance with th previously determed form 0iw the invention. A chamber .35 ha in end o ening, 2"! s secured in thecen: tral space between the inner'ends of the blades be recess a el i a ir of an eerews 33 whic 95.5% l ti H??? 5 i e-v s d 9. .1 the Quieiilfizqf W ti i i 9 ham e 'iii Pra- Vldedwith are "1e range 33/ suitably fastefiedby lcrew'f shoyiin'td permit the insertion and remova Q e e ilbi d seismi a deflector assemb r- '-The.eo ,ki nedi ed Spout an. "de at as em l Weeds imbue-h the p as the ital a reed p rq ieed w t a's'pout portion dito which si-ve is supplied, and which discharges i'n'si-de of the chamber. Formed on the outside-oi the deflector assembly is a hel ic'a'ldeflector flange '42 w-hich terI-ninates adjacent the 'l e f t end of the chamber. The chamber isprovidedwith a plurality ofopenings 43 forwardly of each blade B, and through which the abrasive deflected by. member. 42 is,-discharged. As. s'eenin Rig. 4, spout; M discharges the abrasive into chamber 36 between deflector .exerts'a minor or light'following action upon members flandxfil, the latter being preferably a flange or substantially nopitch extending" only part way around the deflector-assembly. The abrasive deflected by member 42 -is accordingly successively discharged through openings fl3-in'front of each blade as the blade passes a predetermined pointin the rotationof-the-rotor,f and the machine'accordingly effects'a're- I stricted'discharge of thejabrasive in arnanner similar to'the vapparatusshown in FigsQl and 2. Flange. prevents abrasive from inadvertently 'or I prematurely splashing into the discharge". ports 43;. Deflector flange 42. is preferably made of increasing radius toward discharge ports '63 in much the same manner asflange 21 of Fig. I. In Fig. 6, I have illustrated the interior of the chamberand aportion of deflector flange 42 in v developed form to illustrate the manner. in which the abrasive is progressively. propelled toward discharge ports 43, and-successively discharged. therethrough onto the inner ends of the blades. Itis to be understood that the term .discharge edge-.as employed in the description and app'endedclaims applies to discharge edge 22 of theembod'iment shown in Figs. 1 to 3, inclusive, and also to discharge.ports. 43 "of the form of the invention shown in Figshl to- 6, inclusive.

In Figs'..7 to 10, inclusive, I have shown 'afoim of feeding assembly somewhat similar to those shown in Figs. l to 6, with the exception that -a major portion of'a chamber 50 is located-outside the centralspace defined by the inner ends of the zrrhe; Ideflector assemblyiiunctions in a manner similar toisithos'e. previously described and. em-

bodiesiahelical deflecting member 12 of increasing radius 'for dislodging', or deflecting, the abra-I sive from theLchambe' and for causing it to discharge, asindicated .by: arrows 13 in Fig. 10', 1

guard 14: may be provided to cooperate with the discharge from the chamber, as shown'in Fig. 10, to prevent any prematurelyfdischarging abrasive, indicatedbyarrows15, from. entering the blades in otherfthan the proper pick-up zone. Guard 14.

is provided with-asupportifi which is secured toone of arms 6| by means'of nut and boltassem-u blies 63. 1.

blades, and the chamber and the deflector as-f sembly are secured in placeih a'differe'nt manner. The rotor and blade construction i s*gen-' erally the same as that shown in-Figpl, and 'fit-= ting within a'central opening in the rotor and secured tohub in through a spacer disc 46 and cap screws 41 is a flange portion 480i a'shaft or support 43. 41

The chamber is generally cylindrical and is provided with adischarge edge 5| as in the other forms of the invention. The rear end of the chamber-is partially closed by a flange 52 to minimize abrasive leakage, and to enable the abrasive to be built up to its anglejof repose. Projecting inwardly from the inner wall of chamber 59 are a plurality of supports 53 which generally assume the form of bladesfthe supports being joined in the center by a discportion 55 which is secured to the end ofshaft 49 by a cap'screwifi It is tube-understood thatcertain features-of' the-variousforms of theinvention maybe used. with, or substituted for, certain features of other forms,v of the invention. For instance, if desired the discharge edge of thechamber in the .form' of. the invention last described vmay be provided with openings or ,ports, as shown in.Figs. 4; 5, and 6,; without departing fromthespirit of the invention.

It is to be understood that the.- invention may be embodied, in-.-specific :forms other than. that illustrated without departing from the principle. or essential characteristics thereof. The em-l bodiments shown are therefore to be considered:

as illustrative and not, restrictive, the scope 'of the inventionbeing defined by the. appended claims rather than'the foregoing description and" drawings All modificationsand changes which come Within the meaning and range of equivalency of theclaimsare therefore intended to be. included therein. I r

7 1. In anabrading apparatus, a rotor having a plurality "of outwardly extending abrasive .pro-.

The chamber isaccordingly mounted for positive rotation with the {rotor and abrasive is fed thereto by meansof afeedspout 51 having a curved'lower end projectinginto the opening provided by fiange'52. 3

. The abrasive is adapted to be deflected from the inner'wa-ll of the chamber inmuclithe same manner as, previously described inconnection" housing. By loosening nuts H, the'defiector asslernbly, may be rocked'so as'to varythedirection It is to be. understood that the pre-..

of discharge. viously described formsof theinventionmay also be provided with-suchadjustment means...

ends sufi'iciently. radially distant from the axis of the rotor to propelthe abrasive at an abrading velocity, a centrally disposed chamber having a substantially; cylindrical'wall to provide -a sub-' stantial capacity for abrasive relative to the angle of repose, and mounted" for synchronous rotation with saidrotor, and having "an inner wall off arelatively. smalldiameter so that abrasive thereon travels at lessv than .an abrading velocity, means for supplying abrasive into an outer end of said chamber. and. stationarily supported means having ahelical surface for causing abrasive accumulating in said chamber to be moved towards the inner end of the chamber and discharged from said chamber onto said blades adijjacent the-inner ends thereof at a predetermined point in therotation of said rotor, said helical surface increasing .in radius as it approaches the. discharge .end of saidchamber, said rotorcomprising at least: one disc mounted on a shaft, and said chamber being located between said disc and the point'at which abrasive is delivered lindrical chamber mounted forrotationiwith; said rotor substantially'concentric of the .axis 01 said rotor, one .end of said chamberterrninating adiacent saidblades to constitu'te'a dischargeedge for abrasive, means to feed abrasive .into the opposite end of-said chamber and allow it to build up centrifugally on thei 'inner surface thereof, and means for deflectinga portion of them:- cumulated abrasive from the chamber onto said blades adlacentthe inner endssthereof at a. pre-- determined point. in the rotation of saidrotor;

. 3-... In an abrading apparatus, a rotor having a plurality of outwardly extending abrasive. pro-- polling blades, a centrally located and substan-- tiallveylindrical chamber mounted for-rotation with said rotor substantially concentric oi the of said rotor, one end of said chamber terminating adjacent said blades to constitutea discharge edge. for abrasive, the opposite end of said chamber" having an inwardly tapered wall to define a portion of a hollow cone whereby abrasive collected against the inner Wall of said chamber will build up to anangle of repose facing the; discharge endof said chamber, means to feed abrasive into the tapered wall-end of saidohamber and allow it. to build up centrifugally on the inner surface thereof, and means for defleeting a portion of the collected abrasive from said chamber onto. said blades adjacent-the inner ends thereof at a predetermined pointin therotation of said rotor. g

. 4.. In an abrading apparatus: a rotor having a plurality of outwardly extending abrasive pro-- pelling' blades of a length to dispose theirouter endssufiiciently radially distant from: the axis 011 the rotor to propel; the abrasive at an-abrading velocity, a centrally located and substantially cylindrical; chamber mounted for rotation with said notor' substantially concentric of the axisofsaid rotor; one end of said chamber terminating ad jacent said blades to'constitut'e a: discharge edge for abrasive, a stationary feed spout to--feed abrasive into the opposite end of said chamber, and meansmounted on saidfeed'spout for deflecting a po tion of the acbumulatediabrasive from the. chamber onto saidbladesladjacent the inner ends thereof. at a. predetermined point in tl'ie rotation QfSaidiIUIOlI. i 5. Inan abrading apparatus, a rotor 'having a plurality: of abrasive" propelling blades: provided thereon, a centrally located "chamber 'mounted for synchronous. rotation; said rotor, mean's' forgintroducing. abrasive into said 'chamber and allowing it, to build. up centrifugally: on the inner surface thereof, means for deflecting ai per-tion oi th accumulatedi abrasive: from the chamber ontosaidblad'es adj'acentsthe inner ends thereofat a; predetermined point: i'n'the rotation: oi'said rotonsaid chamber. being. provided witha phi-- rality of discharge openings equalinnumber to inner, ends thereof at a-.predeter-mined poinhin. the rotation of the rotor, said chamber being-.-

Provided, with a plurality. of discharge openings qual vin inumbe to saidblades;forwardlygoi each;

lattengand the portions of said chamber between said openings preventing thedischarge of abra: sive at other points in the spaces between said blades.

'7. In: anabrading apparatus, a rotor having a plurality of abrasive propelling blades thereon, a centrally located and substantially. cylindrical chamber closed at one end and open atthe oppo site end and mounted for rotation with said rotor substantially concentric with. the axisqof said rotor, thcclosed end. of said chamber being. adjacent. said blades, the side wall of said chamber adjacent. said blades being provided with a series of openings equal in number to the number. of blades on said rotor, means to feed abrasive into the open end of said chamber and allow it to build up centrifugally on; the inner surface thereof, and means to' deflect abrasive: in said chamber through said openings and onto said blades 'ad.-' jacent the inner ends thereof at a predetermined point in the rotation of saidroto-iz 8. In an abrading apparatus, a rotor having a plurality of abrasive propelling. blades thereon, a centrally located. and substantially cylindrical chamber closed at one end and open at the opposite end and mounted. for rotation with said rotor substantially concentric with the axis of said rotor, the closed end of said chamber being adiacent said blades, the side wall of said chamber adjacent said blades being provided with a series ofopenings equal in number to the number of blades on saidrotor, means to feed abrasive into the open end of said chamber and allow itto buildup centrifugallyon the-inner surface-there- 0.15, means to deflect abrasive in said chamber through said openings andonto saidblades adjae centthe inner ends thereof at apredetermined pointin the rotation. of said rotor, and means to preventthe discharge of abrasive through. said openings at points other than said predetermined point. r

9'. In. anabrading apparatus, a rotor having-aplurality-of abrasive propelling blades thereon, a centrally. located and substantially cylindrical.

chamber closed at one end and-open at the other 1 end andv mounted for rotation with said rotor substantially concentric with: the axis of saidrotor, the-closed end ofsaid chamber being adiacent said bladeathe sidewall of said chamber adjacentsaid blades being provided with a series. of openings equal in number to the" number of: blades on said rotonmeanstofeedabrasive into the open end otsaid-chamber' and allow it to: build up centrifugallyon the-winnersurface'there of, andmeans'to; deflect-abrasive in: said-chamber I ll. The combinationclaimed-in cl'aim 9 where in asecond. flange of substantially no pitch is provided around a portion of saidrelement adjacent said openings: to prevent the discharge. of abrasive; through. said. openings except at the predeterminedzpointiir the? rotation of :said rotor;

bl ejthrough-which. the' abrasivedsied. to'tlie: 12. Inz'ani abrading. apparatusia rotorhavi'n'g" maturely discharged abrasive from being discharged onto said blades at other than said pre-. determined point. g

'16. In an abrading apparatus, a rotor having a fplurality of abrasive propelling blades provided at said open end being partially closed to enable the abrasive to be built up to an angle of repose facing toward the closed end of said chamber,

and means to deflect abrasive'in said chamber through said openings and onto said blades adjacent the inner ends thereof at a'predetermined pointin'the rotation of said rotor.

13. In an abrading apparatus, arotor having a plurality of abrasive propelling blades provided thereon, the inner ends of said blades being spaced apart to define a central opening, a shaft.

in said central opening fixed to said rotor to rotate therewith, chamber fixed to the end of said shaft to rotate a substantially cylindrical thereon, the inner ends of said blades being spaced apart to define a central opening, a shaft in said central opening fixed tosaid rotor to rotate therewith, chamber fixed toand extending over theend of said shaft to rotate'therewith, said chamber having an open end adjacent the inner ends of said blades whereby the edge of the wall of said chamber at said open. end constitutes a discharge edge for abrasive, means to feed abrasive into said chamber, a stationary housing, and a helitherewith, said chamber having an open end adjacent the inner ends of said blades whereby the edge of the wall of said chamber-at said open end constitutes a discharge edge for abrasive,

means to feed abrasive into'said chamber, and means in said chamber to deflect abrasive therefrom over said discharge edge onto the inner ends of said blades at a predetermined point in a the rotation of said rotor. y

14. In an abrading apparatus, a rotor having a plurality of abrasive propelling blades provided thereon, the inner ends of said blades being spaced apart to define a central opening, a shaft in said central opening fixed to said rotor to rotate therewith, a substantially cylindrical chamber fixed to the end of said shaft to rotate therewith, said chamber having an open endedjacent the inner ends of said blades whereby the edge of the wall of said chamber at said open end constitutes a discharge edge for abrasive, the opposite end of said chamber being formed with an inturned flange whereby abrasive supplied to said chamber when the latter is rotating builds up on the walls thereof byreason" of centrifugal force with an angle of repose inclined toward said discharge edge, means to feed abrasive into said chamber, and means in said chamber including v in the rotation of saidrotor.

cal blade supported on said housing concentri- "cally of said shaft and within said chamber to deflect abrasive therefrom over said discharge edge onto the inner ends of said blades at a predetermined point in the rotation of said rotor.

17, In abrading apparatus, a rotor having a plurality .of outwardly extending abrasive propelling blades of *a length to dispose their outer ends sufficiently radially distant from the axis of the rotor to propel the abrasive at an abrading velocity, a centrally located and substantially cylindrical feed chamber mounted for rotation with said rotor with the axis thereof substantially in alignment with the axis of said rotor,

means for supplying abrasive in one general direction into one end of said chamber and allow it,

to; build up centrifugally in the same general direction onthe inner surface thereof, and means for deflecting a portion of the accumulated abra-' .sive towards an opposite-end of the chamber and from the feed chamber onto said blades adjacent the inner ends thereof at a predetermined point 18. Inabra'dingapparatus, a rotor having member mounted for rotation with said rotor,

, means for introducing abrasive into said cylindrical member and allowing the abrasive to build v upcentrifugally on'the in er'surface thereof, said cylindrical member having a peripheral opening a stationary helical blade to deflect abrasive therefrom over said discharge edge onto the'inner." I

ends of said blades at a predetermined point in the rotation of said rotor.

15. In an abrading apparatus, a rotor having a plurality of abrasive propelling blades provided thereon, the inner ends of said blades being spaced apart to define a central opening, a shaft in said central opening fixed to said rotor to rotate, therewith, a substantially cylindrical chamber fixed to the end of said shaft to rotate therewith, said chamber having anopen end 'adjacent the inner ends of said blades whereby the edge of the wall of said chamber at said open end constitutes a discharge edgefor abrasive,

r tion of said support .to rotate therewith, said chamber having a discharge edge adjacent the means to feed abrasive into said chamber, means 7 in said chamber to deflect abrasive therefrom over said discharge edge onto the inner ends of said blades at a predetermined point in the rotatherein forwardly of each blade, and means for deflecting, a portion of the accumulated abrasive for movement through said openings onto said blades adjacent the-inner ends thereof at a predetermined point in the. rotation of said rotor.-

" -1 9." In abrading apparatus, a rotor having a plurality of abrasive propelling blades provided thereonwith the inner ends thereof defining a central opening, a support extending axially through"said central, opening and fixed to said rotor to rotate therewith, a substantially cylindrical feed chamber carried by an outer porinner ends'of said "blades, means for, supplying "abrasive into said feed chamber, and means in said feed chamber to deflect abrasive therefrom over said discharge edge onto the inner-ends of I said blades at a predetermined pointin the rotationof said rotor. 1

r r WALTER L. KEEFERQ tion of said rotor, and means adjacent the outer a periphery of said discharge edge to prevent prea substantially cylindrical ,a plurality of abrasive propelling blades provided thereon,- a centrally located hollow cylindrical 

